1. Field of the Invention
The present invention relates to an ejector refrigeration cycle, which includes an ejector.
2. Description of Related Art
Previously, as a vapor compression refrigeration cycle, an ejector refrigeration cycle, which uses an ejector that serves as a refrigerant depressurizing means and a refrigerant circulating means, has been proposed in Japanese patent No. 3322263.
In Japanese patent No. 3322263, a first evaporator is connected to a refrigerant outlet of the ejector, and a gas/liquid separator is connected to a refrigerant outlet of the first evaporator, and a second evaporator is connected between a liquid phase refrigerant outlet of the gas/liquid separator and a refrigerant inlet of the ejector.
In contrast to the above cycle, an ejector refrigeration cycle shown in FIG. 15 has been proposed in Japanese Unexamined Patent Publication No. 2005-308380 published on Nov. 4, 2005 (corresponding to US 2005/0178150 A1 and US 2005/0268644 A1). In the ejector refrigeration cycle of Japanese Unexamined Patent Publication No. 2005-308380, a branch passage 16, which is branched on an upstream side of an ejector 14 and is connected to a refrigerant inlet 14b of the ejector 14, is provided, and a throttle mechanism 17 and a second evaporator 18 are provided in the branch passage 16.
In the case of Japanese Patent No. 3322263, the refrigerant is drawn into the second evaporator only by the refrigerant suction force of the ejector. Thus, a cycle pressure difference becomes small. In such a case, under a specific operational condition where the input of the ejector 14 becomes small, the refrigerant suction force of the ejector is reduced, and thereby the refrigerant flow quantity of the second evaporator is reduced.
In contrast to this, in the ejector refrigeration cycle of Japanese Unexamined Patent Publication No. 2005-308380, the second evaporator 18 is arranged parallel to the ejector 14, so that the refrigerant can be circulated to the second evaporator 18 using both of the refrigerant suction force of the ejector 14 and the refrigerant suction/discharge force of the compressor 11. Therefore, even under the specific operational condition where the input of the ejector 14 becomes small, the required refrigerant flow quantity of the second evaporator 18 and thereby the required cooling performance of the second evaporator 18 can be easily ensured. At the same time, the refrigerant flow quantity of the second evaporator 18 can be easily adjusted by the dedicated throttle mechanism 17.
In the refrigeration cycle of Japanese Unexamined Patent Publication No. 2005-308380, the refrigerant evaporating pressure (the refrigerant evaporating temperature) becomes lower than that of the first evaporator 15 by the amount, which corresponds to the pressure increasing effect of the ejector 14. As described above, by reducing the refrigerant evaporating temperature of the second evaporator 18, the cooling performance of the second evaporator 18 can be improved.
In the refrigeration cycle of Japanese Unexamined Patent Publication No. 2005-308380, when the refrigerant quantity supplied to the second evaporator 18 of the low temperature side is excessively large, the liquid phase refrigerant, which has not been evaporated through the second evaporator 18, is drawn into the ejector 14 and is then evaporated through the first evaporator 15. In contrast, when the refrigerant quantity supplied to the second evaporator 18 is insufficient, the advantageous feature of the second evaporator 18 (i.e., the lower refrigerant evaporating temperature of the second evaporator 18 in comparison to the first evaporator 15) cannot be utilized, and thereby the cooling performance of the second evaporator 18 is reduced. Therefore, it is important to supply the sufficient amount of refrigerant to the second evaporator 18 without causing the shortage of the refrigerant in the second evaporator 18 to improve the performance.
For instance, in a case where an expansion valve, which is a known typical throttling means, is used as the throttle mechanism 17 of the second evaporator 18, the expansion valve rapidly reduces the throttle opening, so that the refrigerant passage cross sectional area for achieving the predetermined amount of pressure reduction becomes small. Thus, the flow quantity of the refrigerant passing through the expansion valve tends to be reduced, and thereby the performance of the second evaporator 18 is reduced.
Furthermore, in the expansion valve, the refrigerant passage cross sectional area is reduced, so that the refrigerant passage of the expansion valve can be easily clogged with an obstacle. The clogged obstacle significantly reduces the performance.